Portable electronic devices, such as a radio pager or a remote control unit which are in common use, require a decoder or coder which is unique to a particular code signal. Such devices are provided in a housing which contains the electronic components and a battery for energizing the same which can be replaced through an opening in the housing. The decoder (or coder) may include a code plug having the elements to condition the decoder for response to the individual code. In prior devices, it has been necessary to open the housing to set the decoder for a particular code, as by inserting a code plug or by making particular connections, switch settings, or the like. This is objectionable as such access to the components of the device by the user has caused problems when the user has attempted to adjust the device without having adequate knowledge of the same. It is, therefore, desired to be able to change the code for the device without disassembly of the same. Also, it may be desired to change the mode of operation of the decoder (or coder) for use in various coding elements. However, this cannot be easily accomplished in presently known devices.
It has been proposed to provide a slot or opening in the housing of a device for insertion of a plug-in control module, but this is objectionable in a small portable device which is subject to relatively rough outdoor usage. This may allow the entry of foreign material which can interfere with proper operation of the device and cause deterioration thereof.